1. Field of the Invention
The present invention relates to a rotary electric machine, and more specifically, to a brushless motor desirably used as a fan motor in a freezing/refrigerating showcase or a refrigerator.
2. Description of the Related Art
In a freezing/refrigerating showcase such as an open showcase or the like, as can be seen in, e.g., Japanese Patent Application Publication No. H10-019446, a machine room in which a freezer and a fan are arranged is provided on a bottom portion of a showcase body. Above the machine room, there is provided an open-front showroom in which product display shelves are arranged in multiple stages. Cold air generated in the freezer is fed to a circulating duct by a fan and is blown from the upper portion of the showroom toward a front opening, thereby forming an air curtain for keeping the products displayed on the product display shelves cold.
In this showcase, a cold air circulating fan is arranged under an environment in which dew condensation easily is generated due to a temperature difference. For that reason, a motor for rotating fan blades needs to employ a waterproof structure. Conventionally, as can be noted in, e.g., Japanese Patent Application Publications No. H10-304640 and 2008-259370, a motor case is divided into two casings. A sealing means such as an O-ring or the like is interposed between the mating surfaces of the divided casings. As a waterproofing means for lead wires led out from a motor, a grommet is mounted to a lead wire outlet formed in the motor case. The lead wires are drawn out through the grommet.
In the conventional waterproof structure for a motor, as set forth above, the motor case is divided into two casings and the sealing means is interposed between the mating surfaces of the divided casings. However, the mating surfaces for holding the sealing means in place become structurally complex. Moreover, it is hard to say that a sufficient waterproof measure is taken with respect to the portions other than the mating surfaces. Thus, a demand exists for improvement. Particularly, in Japanese Patent Application Publication No. H10-304640, the motor case is provided with a drain hole and a cutoff wall. However, this structure is not capable of reliably preventing infiltration of moisture. In Japanese Patent Application Publication No. 2008-259370, there is disclosed a structure in which a groove-shaped mounting portion is formed in a lead wire outlet portion of a motor case and in which an outer circumferential portion of a grommet is fitted to the groove-shaped mounting portion. However, it is likely that a dimensional error may be generated in the groove-shaped mounting portion of the lead wire outlet portion or a gap may be generated between the lead wire outlet portion and the grommet due to a degradation of the grommet over time. This poses a problem in that the waterproof effect becomes lower.